Oat genotypes exhibit valuable and reproducible polymorphism in the avenin pattern which is important to identify genotypes and to use in breeding programs. Therefore, in this study, 196 Turkish oat landraces (Avena sativa L.) and three commercial cultivars (Checota, Faikbey and Seydişehir) were identified using the SDS-PAGE technique based on oat avenin protein band numbers and molecular weights. Results indicate that genotypes varied in avenin protein band numbers and molecular weights. Avenin protein band numbers and molecular weights ranged from 4 to 16, and 8.8 to 45 kDa, respectively. The bands having the highest molecular weight (45 kDA) was obtained from E19 and E45 genotypes, while the bands having the lowest molecular weights were obtained from A76, A81, A79, E20 and A29 genotypes (8.8, 9.2, 9.5, 9.6 and 9.8 kDa, respectively). A18, A34 and K3 genotypes had the lowest avenin bands (4), while E20 and A54 genotypes had the highest avenin bands (15 and 16, respectively). According to genetic similarity analysis based on avenin protein band numbers and molecular weights, oat genotypes clustered in two major groups at 0.240 genetic similarities. The first major group consisted of A53, E37, E59, A23, A34, and A41 genotypes. In this group, A23-A41 and A53-E37 genotypes were similar with 0.801 and 0.767 coefficients respectively. The second group consisted of three large groups and several small groups. The genotypes clustered in many groups with a large number of genetic similarity coefficients. A2-E57 and K13-K35 genotypes were the most similar with 0.920 genetic similarity coefficients.